1. Field of the Invention
This invention relates to a scroll-type fluid machine, and more particular to, a scroll-type fluid machine applied to compressors, pumps or blowers for a refrigerating system or an air-conditioning system.
2. Description of the Related Art
FIG. 7 is a side cross-sectional view of a conventional scroll-type fluid machine and FIG. 8 is a primarily plan view showing operation of the machine. In FIG. 7, reference numeral 1 refers to a fixed scroll having a scroll portion 1a illustrated in FIG. 8. Denoted by reference numeral 2 is a moving scroll which has a scroll portion 2a illustrated in FIG. 8. Further, reference numeral 3 refers to a compression space having a shape of substantial lunette, which is formed by the scroll portions 1a and 2a. Reference numeral 4 refers to a discharge opening through which fluid is discharged after being compressed in the compression space 3, reference numeral 5 refers to seal elements disposed at end portions of the scroll portions 1a and 2a for sealing the compression space 3, reference numeral 6 refers to a moving scroll shaft, reference numeral 7 refers to a moving scroll shaft bearing for supporting the shaft 6. The moving scroll shaft bearing 7 is disposed in a cylindrical portion 2c jutting from an end plate 2b of the moving scroll 2.
Further, reference numeral 8 is a crank shaft which is eccentrically connected to the moving scroll shaft 6, reference numeral 9 refers to a balancing weight for recovering balance caused by centrifugal force of the scroll, reference numeral 10 refers to a crank shaft bearing, reference numeral 11 refers to a motor, reference numeral 12 refers to a driving shaft for driving the crank shaft 8, reference numeral 13 refers to a housing to which the fixed scroll 1, the crank shaft bearing 10, the motor 11 and the like are fixed, and reference numeral 14 refers to an Oldham's ring for engaging the moving scroll 2 and the housing 13 with each other in the direction that the Oldham's ring 14 crosses them at right angles to prevent the moving scroll 2 from rotating on its own axis.
Next, the operation of the machine will be explained.
When the crank shaft 8 is driven, which is connected to the driving shaft 12 of the motor 11 and is eccentrically connected to the moving scroll shaft 6, the moving scroll 2 is orbited without rotating on its own axis due to the Oldham's ring 14. Then, the scroll portions 1a and 2a of the fixed scroll 1 and the moving scroll 2 respectively engage with each other eccentrically to form at least one compression space 3.
As shown in FIG. 8, when the moving scroll 2 orbits from 0.degree. to 360.degree. in the direction that the arrow shows in the figure, at least one compression space 3 formed at the periphery of the machine moves toward the center thereof, for causing the fluid to be compressed.
Japanese Patent Publication Kokoku Heisei 1-35195 discloses a conventional scroll-type compressor.
In the conventional scroll-type fluid machine with the structure described above, the moving scroll shaft bearing 7 is fixed at the cylindrical portion 2c on the end plate 2b of the moving scroll 2 or in the end plate 2b. Since the center of gravity of the moving scroll 2 itself is positioned on the scroll portion 2a, the moving scroll 2 oscillates about the moving scroll shaft bearing 7 in the direction described by the arrow between the two positions shown by the broken lines as shows in FIG. 9. As a result, a problem is that the scrolling portion 1a of the fixed scroll 1 and the scroll portion 2a of the moving scroll 2 collide with each other to generate noise and wear of the portions in contact. In such a case, a composite vector of the thrust force and the centrifugal force generates an upsetting moment, for causing the scroll portion 2a to be oscillated. To prevent the oscillating motion, a thrust bearing may be installed at the periphery of the moving scroll 2. However, in case that the thrust force is relatively small, the countermeasure cannot be applied to prevent the oscillation.